In conventional practice, supermarkets and convenience stores are equipped with refrigerated merchandisers, which may be open or provided with doors, for presenting refrigerated products like fresh food or beverages to customers while maintaining the fresh food and beverages in a refrigerated environment. Typically, cold, moisture-bearing air is provided to a product display area of the merchandiser by passing an airflow over the heat exchange surface of an evaporator coil containing a suitable refrigerant. As the airflow passes through the evaporator coil, heat is transferred from the airflow to the refrigerant, which causes the refrigerant to evaporate. As a result, the temperature of the air passing through the evaporator is lowered for introduction into the product display area of the merchandiser.
Typically, the temperature of the air discharged into the product display area is controlled to maintain a pre-determined set point. Such a set point is typically recommended by the manufacturer of the refrigerated merchandiser, and is typically based upon data accumulated during experimental trials.